The present invention relates to a small zoom lens system for use with compact cameras that has a smaller constraint on its back focus than a zoom lens for use with single-lens reflex cameras.
Heretofore, a class of two-group zoom lens systems that do not employ aspheric surfaces have been used with compact cameras. An example of these types of systems is one in which the first lens group is composed of several elements, and the second lens group is composed of about three elements. Thus, the exemplary system has about eight elements (see commonly-assigned Japanese Patent Laid-Open Publication No. SHO 62-264019).
Another class of conventional zoom lens systems for use with compact cameras includes one that uses numerous aspheric surfaces and in which the first and second lens groups are each composed of two elements, thereby resulting in a system having four elements total (see commonly-assigned Japanese Patent Laid-Open Publication No. HEI-3-127008), as well as one which is composed of fewer lens elements, such as two or three in total number.
However, the conventional zoom lens systems for use with compact cameras have had various problems. Two-group systems that do not use aspheric surfaces need so many lens elements that making the system compact is difficult.
With four-element systems that have numerous aspheric surfaces, it is difficult to attain balance between reduction in the overall lens length and correction of chromatic aberrations.
Two- or three-element systems have a generally poor performance. Furthermore, it has been difficult to attain balance between reduction in the overall lens length and correction of chromatic aberrations.
Therefore, an object of the present invention is to provide a zoom lens system for use with compact cameras which is compact (i.e., has relatively fewer lens elements) and yet which effectively corrects chromatic aberrations.